1. Field of the Invention
The present invention relates to a zoom gesture determination method and touch control chip, and more particularly, to a zoom gesture determination method and touch control chip that can be utilized in a self-capacitative touch control device.
2. Description of the Prior Art
A touch control device has the benefits of ease of operation, fast reaction and space efficiency. These features allow users to perform operations more intuitively and conveniently; consequently, touch control devices have become important input interfaces that are widely utilized in various consumer electronic products. Specifically, a touch control device utilizes a detection circuit to detect electrical signals of a matrix composed of a plurality of wires, and convert the electrical signals into digital detection data values to determine a touch event. A conventional touch control device is mostly suited for single touch point operations, and faulty determination may occur in multiple touch point operations.
Please refer to FIG. 1, which is a schematic diagram of a projected capacitive touch sensing device 10 of the prior art. The projected capacitive touch sensing device 10 includes sensing capacitor strings X1-Xm and Y1-Yn. Each sensing capacitor string is a one-dimensional structure formed by connecting a plurality of sensing capacitors in series. The conventional touch sensing method detects the capacitance in each sensing capacitor string to determine whether a touch event occurs. The sensing capacitor strings X1-Xm and Y1-Yn are utilized to determine vertical and horizontal touch events, respectively. In the case of horizontal operations, assume the sensing capacitor string X1 has Q sensing capacitors, and each sensing capacitor has a capacitance of C. Under normal circumstances, the sensing capacitor string X1 has a capacitance of QC. If a difference in capacitance caused by a human body (e.g. a finger) touching a sensing capacitor of the sensing capacitor string X1 is ΔC, it can be inferred that the finger is touching a certain point on the sensing capacitor string X1 when the capacitance of the sensing capacitor string X1 is detected to be greater than or equal to “QC+ΔC”. For multi-touch operations, as shown in FIG. 1, where two fingers concurrently touch the projected capacitive touch sensing device 10, the sensing capacitor strings X3, Xm−1, Y3 and Yn−1 will concurrently sense capacitance variations; thus, it is determined that touch events occur at all points (X3, Y3), (X3, Yn−1), (Xm−1, Y3) and (Xm−1, Yn−1). In fact, only (X3, Y3) and (Xm−1, Yn−1) are real touch points, whereas (X3, Yn−1) and (Xm−1, Y3) are not. This faulty determination of the projected capacitive touch sensing device 10 leads to a detection error where two nonexistent touch points are registered, causing what is known as the “ghost key” phenomenon. Therefore, for multi-touch operations, it is only possible to determine which intersections of the sensing capacitor strings the touch event may have occurred at, instead of a precise and definite touch point.